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.TH SCHED_SETSCHEDULER 3C "Nov 26, 2017"
.SH NAME
sched_setscheduler \- set scheduling policy and scheduling parameters
.SH SYNOPSIS
.LP
.nf
#include <sched.h>

\fBint\fR \fBsched_setscheduler\fR(\fBpid_t\fR \fIpid\fR, \fBint\fR \fIpolicy\fR,
     \fBconst struct sched_param *\fR\fIparam\fR);
.fi

.SH DESCRIPTION
.LP
The \fBsched_setscheduler()\fR function sets the scheduling policy and
scheduling parameters of the process specified by \fIpid\fR to \fIpolicy\fR and
the parameters specified in the \fBsched_param\fR structure pointed to by
\fIparam\fR, respectively. The value of the \fBsched_priority\fR member in the
\fBsched_param\fR structure is any integer within the inclusive priority range
for the scheduling policy specified by \fIpolicy\fR. The
\fBsched_setscheduler()\fR function ignores the other members of the
\fBsched_param\fR structure. If the value of \fIpid\fR is negative, the
behavior of the \fBsched_setscheduler()\fR function is unspecified.
.sp
.LP
The possible values for the \fIpolicy\fR parameter are defined in the header
<\fBsched.h\fR> (see \fBsched.h\fR(3HEAD)):
.sp
.LP
If a process specified by \fIpid\fR exists and if the calling process has
permission, the scheduling policy and scheduling parameters are set for the
process whose process  \fBID\fR is equal to \fIpid.\fR The real or effective
user  \fBID\fR of the calling process must match the real or saved (from
\fBexec\fR(2)) user  \fBID\fR of the target process unless the effective user
\fBID\fR of the calling process is 0. See \fBIntro\fR(2).
.sp
.LP
If \fIpid\fR is 0, the scheduling policy and scheduling parameters are set for
the calling process.
.sp
.LP
To change the \fIpolicy\fR of any process to either of the real time policies
\fBSCHED_FIFO\fR or \fBSCHED_RR\fR, the calling process must either have the
\fBSCHED_FIFO\fR or \fBSCHED_RR\fR policy or have an effective user \fBID\fR of
\fB0\fR.
.sp
.LP
The \fBsched_setscheduler()\fR function is considered successful if it succeeds
in setting the scheduling policy and scheduling parameters of the process
specified by \fIpid\fR to the values specified by \fIpolicy\fR and the
structure pointed to by \fIparam\fR, respectively.
.SH RETURN VALUES
.LP
Upon successful completion, the function returns the former scheduling policy
of the specified process. If the \fBsched_setscheduler()\fR function fails to
complete successfully, the policy and scheduling parameters remain unchanged,
and the function returns \(mi1 and sets \fBerrno\fR to indicate the error.
.SH ERRORS
.LP
The \fBsched_setscheduler()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The value of \fIpolicy\fR is invalid, or one or more of the parameters
contained in \fIparam\fR is outside the valid range for the specified
scheduling policy.
.RE

.sp
.ne 2
.na
\fB\fBEPERM\fR\fR
.ad
.RS 10n
The requesting process does not have permission to set either or both of the
scheduling parameters or the scheduling policy of the specified process.
.RE

.sp
.ne 2
.na
\fB\fBESRCH\fR\fR
.ad
.RS 10n
No process can be found corresponding to that specified by \fIpid.\fR
.RE

.SH ATTRIBUTES
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Committed
_
MT-Level	MT-Safe
_
Standard	See \fBstandards\fR(7).
.TE

.SH SEE ALSO
.LP
.BR priocntl (1),
.BR Intro (2),
.BR exec (2),
.BR priocntl (2),
.BR sched_get_priority_max (3C),
.BR sched_getparam (3C),
.BR sched_getscheduler (3C),
.BR sched_setparam (3C),
.BR sched.h (3HEAD),
.BR librt (3LIB),
.BR attributes (7),
.BR standards (7)
